A sailboard is a modified surfboard having a single sail mounted on a mast that pivots on a ball joint. The rider of a sailboard stands on the top surface of the sailboard. The skeg on a sailboard is located close to the rear of the board. The skeg is a vertical structure, which acts as a lifting body to create lift and stability. The lift of the skeg works with the sail to enable the sailboard to go up wind. The skeg is also referred to as a fin. The sailboard evolved from sailing combined with surfing. The earliest sailboard started as a long board with a dagger board and a skeg much like a sailboat.
The sailboard evolved into a much shorter board with a single skeg in the back. No dagger board is necessary if the board is planing. Other advances have occur to affect the construction of sailboard, including sail size, which has increased form 7 sq. meters to 12.5 sq. meters. Consequently, the bigger sails require bigger skegs; thus, skeg size has increase from 38 cm to 85 cm. This ratio may be approximated by the ratio of the density of water to the density of air. The size of the skeg has increased until the skeg is now as large as prior art dagger boards. The width of the sailboard also increased to support the larger equipment. The single skeg model of sailboards has reached a point of diminishing returns such that the increase of power and lift from the larger sails and skegs is counterbalanced by increased drag and more expensive construction.
Certain prior art patents include descriptions of various efforts to reduce drag in aircraft and foils. U.S. Pat. No. 6,340,134, issued on Jan. 22, 2002 to Meschino describes a wing combination for drag reduction, aircraft including such a wing, and a method of reducing the drag of an existing aircraft. A supplementary wing is used to connect to the main wing of an aircraft to reduce drag. U.S. Pat. No. 5,022,337, issued on Jun. 11, 1991 to Caldwell teaches a lift producing device exhibiting low drag and reduced ventilation potential and method for producing the same. This invention discloses a lifting device for sailboats and sailboards, which have been shaped to reduce ventilation. U.S. Pat. No. 4,949,919, issued on Aug. 21, 1990 to Wajnikonis discloses a foil with high lift and low drag coefficients. The foil disclosed in this patent aims to improve hydrofoil efficiency by reducing the vortex area of the tip of the foil. Furthermore, U.S. Pat. No. 4,090,681, issued on May 23, 1978 to Zimmer teaches an airplane with two superposed wings. As a biplane, the invention uses a rhombic shape frame of the wings to reduce drag.
Sailboards have not used multiple high aspect ratio skegs to reduce induced drag in the past. All race (formula) boards currently use a single skeg. Dual and triple skegs have been used to increase stability and turning ability. The dual skegs used in the past were not large enough to provide good upwind performance. These dual skegs, as used in the past, were low aspect ratio fins. The distance between the fins was not wide enough to reduce the interference drag to acceptable levels. These previous fins designs were not mounted parallel to each other and to the centerline of the sailboard. In certain circumstances, thruster fins have been used to improve jibbing performance. These thruster fins are small fins located close to the outer rail of the sailboard.
In the past, the tail width of all board designs has been too narrow to support the use of dual fins. Current formula board designs are only now approaching a width of 70 centimeters at the tail.
Dagger board have been used since the beginning of sailboarding. All prior art dagger boards have been located in the center of the board between the mast base and the skeg. These dagger boards were intended to work with the skeg.
Previous sailboard designs were too long to aerodynamically stable. It is intended to make the board designs extremely long for high speed sailing in order to minimize aerodynamic lift. The prior art sailboards have not used tunnels formed on the underside thereof to improve aerodynamic stability and lift. Prior art sailboards have a flipped up nose which causes turbulence and increase drag.
It is an object of the present invention to provide a sailboard that enables a formula-type board to be competitive at the low end of the wind range and to increase board speed.
It is another object of the present invention to provide a sailboard which increases competitiveness of the sailboard by planing in light wind and increasing sub-planing performance.
It is an another object of the present invention to provide a sailboard having reduced board drag.
It is a further object of the present invention to provide a sailboard which reduces fin drag to allow higher pointing angles when sailing upwind and faster board speed and deeper pointing angles when sailing offwind.
It is a further object of the present invention to provide a sailboard with a rear-mounted dagger board which allows the sailboard to sail upwind in very light wind.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.